1. Field of the Invention
The present invention relates in general to an image-scanning module. More specifically, it relates to an image-scanning module for downsizing image-scanning devices such as scanners.
2. Description of the Related Art
FIG. 1 shows an image-scanning device of the prior art, which comprises a light-radiating device 14 and a focusing-and-imaging device 16. The light-radiating device 14 may be a cold-cathode tube having a straight line tube 142 and two connecting heads 144 at its ends. The focusing-and-imaging device 16 may consist of a lens set.
The light-radiating device 14 moves with respect to an object 10 which is, for example, a piece of paper or a picture, along a scanning path as indicated by arrow A. The object 10 reflects the light emitted by the light-radiating device 14, as indicated by arrows B. The focusing-and-imaging device 16 then focuses an image of the reflected light onto the image-receiving device 12 as indicated by arrow C. For instance, the image-receiving device 12 may be a charge-coupled device (CCD).
In general, the light emitted from a straight-line light tube is nonuniform. The light intensity emitted from the center of a straight-line tube is stronger than that from the two ends, and thus the luminance at the center of the scanning central line is greater than that at the two ends of the scanning central line. Consequently, the image received by the charge-coupled device suffers distortion, thereby reducing the signal accuracy and scanning quality.
FIG. 2 shows a luminance characteristic curve of a conventional straight-line light tube. In FIG. 2, the length of the straight-line light tube 30 is L, and the luminance values at both ends of the straight-line light tube 30 (segments L2 and L3) drop dramatically. Therefore, only the luminance values in the L1 segment are even and effective (available) for scanning. Because the straight-line tube has the luminance characteristics as shown in FIG. 2, a straight-line tube longer than the actual scanning width is used to provide a sufficiently long effective scanning segment, thereby increasing the size of the scanner. For instance, the length of a straight-line tube (L) is about 262 mm generally, while the length of the effective portion (L1) is about 226 mm. Thus, a straight-line tube of length 262 mm is needed to scan an object of maximal length 226 mm. This restriction is an obstacle to downsizing the scanners.
Lighting tubes as depicted in FIGS. 3(a)xcx9c3(d) have been proposed to overcome the problems of the insufficient luminance at both ends of the straight-line tubes. Each of the tubes as depicted in FIGS. 3(a)xcx9c3(d) comprises a first lighting portion of straight-line shape and two second lighting portions extended from both ends of the first lighting portion. In FIGS. 3(a)xcx9c3(c), the first lighting portion and the two second lighting portions are straight-line shaped, and each of the two second lighting portions is at a specific angle to the first lighting portion. In FIG. 3(d), each of the two lighting portions is U-shaped.
The weak luminance at both ends of each of the first lighting portion (equivalent to a straight-line tube) can be compensated by the two second lighting portion.
FIG. 4 shows an image-scanning device using the lighting tube depicted in FIG. 3(a) as a light-radiating device. The lighting tubes 38 is disposed in parallel with a scanned object 32. The scanned object 32 reflects the light emitted by the lighting tube 38, as indicated by arrows D. The focusing-and-imaging device 36 then focuses an image of the reflected light onto the charge-coupled device 34. The notation LS is the width of a scanning line. In FIG. 4, the lighting tube 38 is arranged in parallel with the scanned object 32. Therefore, the length of the lighting tube 38 (equivalent to the length of the straight-line portion) must be longer than the width of the scanning line LS in order to prevent the reflected light path D from being masked by the L-shaped portions extended from both ends of the straight-line portion of the lighting tube 38. Specifically, the L-shaped portions easily mask the reflected light path D when the lighting tube 38 is disposed close to the scanned object. Thus, the scanner is still bulky due to the restriction on the lengths of the lighting tubes.
Therefore, an object of the present invention is to provide an image-scanning module for downsizing the scanners. The light-radiating device (lighting tube) in the image-scanning module is disposed perpendicular to the plane where the scanned object is placed, thereby preventing the reflected light path from being masked by the extended portions of the light-radiating device. Consequently, a shorter lighting tube can be used, thereby downsizing the image-scanning devices.
In order to achieve the above object, an image-scanning module for downsizing a scanner comprises at least the following units.
A light-radiating device for emitting light to scan an object, comprising a first lighting portion and two second lighting portions extended from two ends of the first lighting portion; wherein the first lighting portion and the two second lighting portions are on the same plane.
A focusing-and-imaging device for focusing the reflected light from said scanned object and for forming an image.
An image receiving device for receiving and processing said image.
The light-radiating device is disposed in a way that the plane formed by the first lighting portion and the two second lighting portions is perpendicular to the plane where the scanned object is placed, whereby the reflected light from said scanned object is not masked by the two lighting portions and the length of first lighting portion can be reduced, thereby downsizing the scanner.